Paint adhesion testing
In the paint and coating industries, paint adhesion testing is often used to determine if the paint or coating will adhere properly to the substrates to which they are applied. Several tests measure the resistance of paints and coatings from substrates: cross-cut test, scrape adhesion, pull-off test, and others.[1]
Scrape Adhesion Test
The scrape adhesion test measures the determination of the adhesion of organic coatings when applied to smooth, flat panel surfaces. It is helpful in giving relative ratings for a number of coated panels showing significant differences in adhesion. The tested materials are applied uniformly to flat panels, mainly some sort of sheet metal. When the materials have dried, the adhesion is determined by pressing panels under a rounded stylus loaded with increasing weight until the coating is removed from the substrate surface.[2]
Pull-off test
The adhesion of a coating or several coated samples of any paint product is measured by assessing the minimum
Cross-cut Test
The cross-cut test is a method for determining the resistance of paints and coatings to separation from substrates by utilizing a tool to cut a right-angle lattice pattern into the coating, penetrating to the substrate.
A quick pass/fail test can be accomplished through this method. When testing a multi-coat system, determination of the resistance to separating different layers from one another can be accomplished.
There are two methods described in the ASTM Specification;[4]
ASTM D 3359 Test Method A
An X-cut is made through the film with a carbide tip tool to the substrate. Pressure-sensitive tape is applied over the cut. Tape is smoothed into place using a pencil eraser over the area of the incisions. Tape is removed by pulling it off rapidly back over itself as close to an angle of 180°. Adhesion is assessed on a 0 to 5 scale.
ASTM D 3359 Test Method B
A crosshatch pattern is made through the film to the substrate. Detached flakes of coating are removed by brushing with a soft brush. Pressure-sensitive tape is applied over the crosshatch cut. Tape is smoothed into place using a pencil eraser over the area of the incisions. Tape is removed by pulling it off rapidly back over itself as close to an angle of 180°. Adhesion is assessed on a 0 to 5 scale. [0- Greater than 65% area removed & 5 is 0% area removed]
See also
- Painter and decorator
Notes
- ^ Mittal, K L (1995). Adhesion Measurement of Films and Coatings. VSP.
- ^ "ASTM D2197 - 98 Standard Test Method for Adhesion of Organic Coatings by Scrape Adhesion NO_PDF". www.astm.org.
- ^ "ASTM Standard for Pull-Off Test". ASTM.
- ^ "ASTM D3359 - 17 Standard Test Methods for Rating Adhesion by Tape Test". www.astm.org.